SSH authentication doesn't appear to work on Windows

[zombiezen]

Running:

gg -show-git pull ssh://git@github.com/gg-scm/gg.git

gives the output:

gg: exec: git config -z --list
gg: exec: git symbolic-ref --quiet HEAD
gg: exec: git show-ref --head
gg: exec: git ls-remote --quiet -- ssh://git@github.com/gg-scm/gg.git
gg: git ls-remote "ssh://git@github.com/gg-scm/gg.git":
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

However, running this works:

git ls-remote --quiet -- ssh://git@github.com/gg-scm/gg.git